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Unread 02-16-2014, 04:00 PM   #1
98poswrangler
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1989 YJ Wrangler 
 
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89 2.5l running issue

hey all, my issue: 2.5l wrangler, fires up fine with a high idle, over 2000, immediately drops to around 800-1000 rpm, when i go to drive it, she starts bucking like its running out of gas and trying to stall. things ive checked: tps, map, crank sensors, fuel pressure, fuel filter, pickup screen, fuel pump 1 yr old but pressure is good, manifold temp sensor, cap n rotor, plugs, replaced to ignition control module as it tested bad at both autozone and discount. when i installed the new icm it ran great at an idle for about 5 mins then started acting up. if i let it stall and do not reset the key switch it will fire up fine for a few more minutes then start acting up again. starting to loose my patience and considering selling it to just be done with it, but i love my jeep. any thoughts? from what ive read there is no diagnostic on this thing and ive checked the sensors using voltage and ohm tests ive found on all the forums. thanks a bunch.

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Unread 02-16-2014, 04:27 PM   #2
98poswrangler
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noticed today while working on the jeep, i plugged the vac line going to the egr valve and tapped on the valve to see if it was stuck open, no change whatsoever, so i focused my attention to the map sensor again, while the jeep is running rough if i unplugg the vac line into the map sensor and put my thumb over the hole, on the line not the sensor, it smooths out but as soon as i plug the line back on it starts stalling out again, could i have a bad map sensor?
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Unread 02-17-2014, 05:39 AM   #3
Que89YJ
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If it idles fine for a while and then goes bad then no it isnt the map. It is probably one of your sensors. My guess would be your O2 sensor. PM senst for the FSM. Try disconnecting the O2 sensor.
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Unread 02-17-2014, 06:02 AM   #4
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^this.

Disconnect the O2 if she runs fine then replace it.
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Unread 02-17-2014, 02:06 PM   #5
98poswrangler
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ok unplugged the o2 sensor, jeep fired up and ran like crap, ie very rough, put it in gear and tried to drive it but as soon as I stepped on the pedal to give it gas it started bogging out like it normally does. as far as it just running rougher it acted exactly the same. let me clarify, it does not stall just sitting at an idle for almost 10 mins, but as soon as I try to drive it, even if its the first attempt for the day, it will start to stall. I unplugged the map sensor vac line and plugged it, after I reset the comp from the o2 test, and tried to drive it, of course it died, but it ran for over 10 mins without a problem at idle. if I unplug the wiring plug from the map sensor it just shuts off. thoughts?
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Unread 02-17-2014, 02:12 PM   #6
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Fuel pressure?
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Unread 02-17-2014, 03:03 PM   #7
98poswrangler
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Fuel pressure is fine even when it is bogging out, ive learned that if I keep working the throttle I can get it to start bogging out.
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Unread 02-17-2014, 03:19 PM   #8
Que89YJ
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You need to use the manual and run the resistance checks on the intake air temp and coolant temp sensor. What's the fuel pressure reading? Does it bleed down when you turn it off?
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Unread 02-17-2014, 03:28 PM   #9
98poswrangler
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Ohms checks have been done on the temp sensors, votage verified on the tps, electricly the map was checked, did not check for a vacuum leak on map, fuel pressure does fall off when you shut it down
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Unread 02-17-2014, 03:55 PM   #10
Que89YJ
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The pressure falling off is either a bad injector or fuel pump.
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Unread 02-17-2014, 04:24 PM   #11
98poswrangler
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I read that only the multiport injection retains pressure which is why it has the bleed valve and that this system only has pressure when running. Thoughts? The fuel pump is about a year old but, I know that means squat, but having good pressure while its trying to stall? Should I recheck all the sensors since I replaced a faulty ignition control module?
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Unread 02-17-2014, 04:56 PM   #12
98poswrangler
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Ok at the request of a friend I changed th vacuum line to the map, said it was squishy, no difference, so one by one I started unplugging things one at a time to check for changes. It seems that as the engine starts to come to temp is when its starts acting up. Upon inital start up the idle is around 3000 rpm then it immediately drops to around 2000, after about 2-3 mins idle then drops to around 1000 rpm and that is when trouble starts. I unplugged the manifold sensor on top of the intake, the one under the throttlebody in the intake and the o2, and although it runs differently it always acts up the same.
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Unread 02-17-2014, 05:00 PM   #13
Mark05059
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you said you checked the coolant temp sensor.. did you check the one near the t-stat housing or the one near the firewall?
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Unread 02-17-2014, 05:34 PM   #14
98poswrangler
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Closer to the firewall on top of the intake, has 2 wires coming out, looks like it is mounted in the intake runner
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Unread 02-17-2014, 05:35 PM   #15
98poswrangler
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I think its the air temp, would the coolant sens interfere with it runnin because I did not check that
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bogging , help needed , stalling

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